1. Field of the Invention
The present invention relates to an electrophoresis type display device, and more particularly, to an array substrate for an electrophoresis type display device, a method of manufacturing the same, and a method of repairing a line of the same.
2. Discussion of the Related Art
Until recently, display devices, such as liquid crystal display (LCD) devices, plasma display panels (PDPs) and organic electro-luminescence displays (OLEDs) have typically been used. Recently, besides the above display devices such as the LCDs, PDPs and OELDs, an electrophoresis type display device is suggested. The electrophoresis type display device has many advantages such as high contrast ratio, rapid response, low price and the like.
FIG. 1 is a schematic cross-sectional view illustrating a principle of operating an electrophoresis type display device.
Referring to FIG. 1, the electrophoresis type display device 1 includes first and second substrates 11 and 36, and an ink layer 57 between the first and second substrates 11 and 36. The ink layer 57 includes a plurality of capsules 63 each of which includes a plurality of white pigments 59 and a plurality of black pigments 61. The white and black pigments 59 and 61 are charged by condensation polymerization. The white pigments 59 have a negative polarity while the black pigments 61 have a positive polarity.
On the first substrate 11, a plurality of pixel electrodes 28 are formed in a plurality of pixel regions, respectively. The pixel electrodes 28 are selectively applied with a positive (+) voltage or a negative (−) voltage. Accordingly, the pigments 59 or 61 having the polarity opposite to the polarity of the pixel electrode 28 move in a direction toward the pixel electrode 28 while the pigments 59 or 61 having the polarity identical to the polarity of the pixel electrode 28 move in a direction away from the pixel electrode 28. Accordingly, according to the polarity relationship of the pigments 59 and 61 and the pixel electrode 28, when the black pigments 61 move in a direction away from the pixel electrode 28, a black color is displayed in the corresponding pixel region. To the contrary, when the white pigments 59 move in a direction away from the pixel electrode 28, a white color is displayed in the corresponding pixel region. This principle makes images displayed through the electrophoresis type display device.
FIG. 2 is a cross-sectional view illustrating the electrophoresis type display device according to the related art.
Referring to FIG. 2, the electrophoresis type display device 1 includes a first substrate 11, a second substrate 36, and an electrophoresis film 60. The electrophoresis film 60 includes an ink layer 57 comprising a plurality of capsules 63, a first adhesive layer 51 on one outer surface of the ink layer 57, a common electrode 55 on the other outer surface of the ink layer 57, and a second adhesive layer 53 on an outer surface of the common electrode 55. The capsule 63 includes a plurality of white pigments 59 and a plurality of black pigments 61. The white pigments 59 are charged with negative polarity while the black pigments 61 are charged with positive polarity.
The second substrate 36 is made of a transparent material, such as plastic or glass. The first substrate 11 is made of an opaque material such as stainless. Alternatively, the first substrate 11 is made of a transparent material, such as plastic or glass.
A color filter 40 including red (R), green (G) and blue (B) color filter patterns is formed on an inner surface of the second substrate 36.
A gate line 12 and a data line 19 crossing each other to define a pixel region P are formed on an inner surface of the first substrate 11. A thin film transistor Tr is formed in the pixel region P. The thin film transistor Tr includes a gate electrode 13, a semiconductor layer 18 and source and drain electrodes 20 and 22. The semiconductor layer 18 includes an active layer 18a and an ohmic contact layer 18b. A gate insulating layer 16 is on the gate electrode 13.
First and second passivation layers 25 and 26 are on the thin film transistor Tr and include a drain contact hole 27 exposing the drain electrode 22. A pixel electrode 28 is formed on the second passivation layer 26 in the pixel region P. The pixel electrode 28 contacts the drain electrode 22 through the drain contact hole 27. The pixel electrode 28 is made of a transparent conductive material, such as indium-tin-oxide (ITO), indium-zinc-oxide (IZO) or indium-tin-zinc-oxide (ITZO).
The electrophoresis type display device 1 uses an external light, such as sun light or room light, as light source. The pixel electrode 28 is selectively applied with a negative or positive polarity voltage. According to the polarity of the pixel electrodes 28, the white pigments 59 and the black pigments 61 moves, and thus images are displayed.
Since the electrophoresis type display device 1 displays images using a reflection property of the ink layer 57, one of the factors increasing a reflectivity is increasing the reflective region. In order to allow the electrophoresis film 60 to function as a reflective medium, a pixel electrode 28 should be used on the first substrate 11. A region covered by the pixel electrode 28 is considered as the reflective region. Accordingly, as a size of the pixel electrode increases, the reflective region increases. Accordingly, in order to increase the reflective region, the pixel electrode 28 is formed to overlap the gate line and the data line 19.
However, when the pixel electrode 28 overlaps the gate line and the data line 19, this causes a parasitic capacitance between the pixel electrode 28 and each of the gate line and the data line 19 to increase, and signals of the gate line and the data line thus delay. To reduce the parasitic capacitance, the second passivation layer 26 made of an organic insulating material is formed on the first passivation layer 25 made of an inorganic insulating material.
However, when the second passivation layer 26 is formed with a thicker thickness, a problem happens in a repair process for the gate line and/or the data line. Particularly, in manufacturing processes, an open circuit of the gate line or the data line 19 due to external particles may occur. Therefore a repair process is performed to solve the open circuit. However, this repair process becomes difficult due to the second passivation layer 26.
FIG. 3 is a cross-sectional view illustrating a repair process for the gate line in the electrophoresis type display device according to the related art.
Referring to FIG. 3, when a gate line 12 on the substrate 11 is open-circuited, the portion of pixel regions P located after an open-circuited portion OC of the gate line 12 may not applied with signals. As a result, a line defect occurs, and so many pixel regions P connected to the defected line may be caused not to be normally operated. To change the line defect into a point defect, a repair process is performed. The point defect is making one or two pixel regions defected.
In more detail, the repair process is performed to form a bypass line by performing a welding process at both sides of the open-circuited portion OC of the gate line 12. In the welding process, a laser beam is irradiated on the both sides of the open-circuit portion OC of the gate line 12, and thus, a pixel electrode 28 and a neighboring pixel electrode 28 are melted, and a second passivation layer 26, a first passivation layer 25 and a gate insulating layer 16 below the both pixel electrodes 28 are removed to form holes 81. The melted pixel electrodes 28 stream down the contact holes 81 and contact the gate line 12. Further, the both pixel electrodes 28 are connected to each other through a connection pattern. Accordingly, the bypass line for the gate line is made through the melted pixel electrodes 28 and the connection pattern.
However, since the second passivation layer 26 is made of an organic insulating material and has a thicker thickness, the welding process is not appropriately performed. In other words, because of the property of the organic insulating material, inner wall surfaces of the contact holes 81 made by removing the second passivation layer 26 are very rough. This roughness disturbs the melted pixel electrode in streaming down the inner wall surfaces of the contact hole 81. Further, since the second passivation layer 26 is relatively very thick, and the melted amount of the pixel electrode 28 is relatively small, it may thus be not enough to cover the entire inner wall surfaces of the contact hole 81. Accordingly, the contact between the pixel electrode 28 and the gate line 12 through the contact hole 81 is not appropriately made, and the repair for the gate line 12 is not completed. This incomplete repair occurs to the data line 18 as well.